Workers Crushed by Collapse of Tank Roof Support Structure

Workers Crushed by Collapse
of Tank Roof Support Structure
Date of Incident:
Type of Incident:
April 24, 2007
Double Fatality
2 Serious Injuries
3 Minor Injuries
TABLE OF CONTENTS
PAGE NUMBER
SECTION 1.0
DA TE AND TIME OF INCIDENT
3
SECTION 2.0
NAME & ADDRESS OF PRINCIPAL
ST AKEHOLDER(S)
- Owner(s)
- Prime Contractor
- Employer(s)
- Stakeholders
3
SECTION 3.0
DESCRIPTION OF PRINCIPAL
STAKEHOLDER(S)
4
SECTION 4.0
LOCATION OF INCIDENT
6
SECTION 5.0
EQUIPMENT AND MATERIAL INVOLVED
7
SECTION 6.0
NARRATIVE DESCRIPTION OF INCIDENT
8
SECTION 7.0
ANALYSIS
12
SECTION 8.0
APPLICABLE LEGISLATION
14
SECTION 9.0
FOLLOW-UP/ACTION TAKEN
17
SECTION 10.0
SIGNATURES
18
SECTION 11.0
ATTACHMENTS
18
2
September 27, 2007
File: F-5 36919
Section 1.0
DATE AND TIME OF INCIDENT
1.1
April 24, 2007, approximately 2:30 p.m.
Section 2.0
NAME & ADDRESS OF PRINCIPAL STAKEHOLDER(S)
2.1
Owner(s)
2. 1. I
Canadian Natural Resources Limited
2500-855 2 Street SW, Calgary, Alberta T2P 41 8
2 .2
Prime Contractor
2.2. l
Canadian Natural Resources Limited Horizon Oil Sands Corporation (CN RL Horizon)
PO Bag 4025 , Fort McMurray, Alberta T9H 3H5
2.3
Employer 1
2.3. 1
SSEC Canada Ltd. (SSEC Canada)
#1800, 250-6 A venue, Calgary, Alberta T2P 3H7
2.4
Employer 2
2.4. l
Tenth Construction Company of Sinopec (TCC)
PO Box # 132, Zibo, Shandong, China 255438
2.5
Stakeholder 1
2.5. 1
Sinopec Shanghai Engineering Company Ltd. (SSEC China)
769 Zhangyang Road, Pudong New Area, Shanghai, China
2.6
Stakeholder 2
2.6.1
China Petroleum and Chemical [Petrochemical] Corporation (Sinopec)
PO Box 3013, Beijing 100011, China
2.7
Stakeholder 3
2.7.1
The Zachry Group
Suite 250, 700 Sixth Avenue SW, Calgary, Alberta, T2P OT8
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2.8
Stakeholder 4
2.8.1
Zachry Energy International Inc.
1238, 13351 Commerce Parkway, Richmond, British Columbia V6V 2X7
2.9
Stakeholder 5
2.9.1
TIW Division of Canadian Erectors Ltd. (TIW)
23 Smith Street, St. Catherine's, Ontario L2R 6Y6
Section 3.0
DESCRIPTION OF PRINCIPAL STAKEHOLDER(S)
3.1
Canadian Natural Resources Limited (CNRL)
3 .1.1
CNRL is a senior independent oil and natural gas exploration, development and
production company based in Calgary, Alberta.
3.1.2
The CNRL Horizon Oil Sands Project is located approximately 70 km north of Fort
McMurray and 30 km north of Fort MacKay, Alberta. CNRL owns and operates
leases covering approximately 115,000 acres and will use open pi t mining methods to
mine oil sands. A plant is being constructed that will separate raw bitumen from the
oil sands and upgrade the bitumen to a synthetic crnde oil using delayed coking and
hydro-treating technologies. Phase 1 started in 2005 and is scheduled for completion
in 2008, ramping up to produce 11 0,000 barrels of synthetic crude oil per day. Phases
2 and 3 wi ll proceed until projected completion in 20 12. Phase 3 is expected to bring
production to 232,000 barrels of synthetic crude oil per day. At the time of the
incident approximately 6,000 workers were working on the construction of the
project.
3.2
SSEC Canada Ltd. (SSEC Canada)
3.2.1
SSEC Canada is an Alberta corporation. The company was incorporated in April,
2006 to bid for work in the Alberta oil sands. The company is 90% owned by SSEC
China, a Chinese company, and 10% owned by Zachry Energy International Inc., a
company based in British Columbia. SSEC Canada uses management, technical and
journeyman workers drawn from SSEC China and Tenth Construction Company of
Sinopec (TCC), working in Alberta as temporary foreign workers, to carry out
projects such as the tank farm project at the CNRL Horizon Oil Sands Project.
3.2.2
SSEC Canada was contracted by CNRL Horizon to construct a total of 14 tanks, 11
on the east tank farm and 3 on the west tank farm at the CNRL Horizon Plant Site.
The effecti ve date of the contract was April 11 , 2006. SSEC Canada was expected to
have workers available July 2006 to commence the tank assembly at the west tank
farm. Work on the three tanks at the west tank fan11 was scheduled for completion by
September, 2007.
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September 27, 2007
Fil e: F-536919
3.2.3
The three tanks on the west tank farm were being constructed in accordance with a
tank erection schedule prepared by CNRL. The schedule specified a sequence of
construction where the tank floors were laid, the walls were started and the internal
roof support structures were erected. SSEC Canada was required to construct the
tanks in accordance with the tank erection schedule, and in accordance witb
component and material schedules and engineered drawings provided by TIW. The
TIW drawings showed how the components and materials they had supplied fitted
together. SSEC Canada was responsible for the direction of their workers, which
included giving instructions on how component parts of the roof support structure
were to be suppotied from movement or falling until the construction was complete
and the tank assemblies were self-supporting.
3.3
Tenth Construction Compan y of Sinopec (TCC)
3.3. l
TCC is an industrial construction company in China, specializing in the construction
and installation of petroleum refining projects. TCC has undertaken construction
projects in Africa, Asia and Saudi Arabia.
3 .4
Sinopec Shanghai Engineering Company (SSEC China)
SSEC China is a Chinese company based in Shanghai, China. SSEC China has the
capacity to undertake mid to large engineering projects including projects in the
petrochemical industry. SSEC China has some contacts with engineering companies
internationally. SSEC China own a 90% share of SSEC Canada and exercises full
control of all activities of SSEC Canada. The Horizon tank project was sub
contracted to TCC by SSEC China. All workers were recruited by TCC. Most
construction management personnel were employed by TCC. SSEC China employed
one business representati ve in Calgary to dea l with the finances and one secretary at
the CNRL site.
3.5
Sinopec China Petroleum and Chemical !Petrochemical! Corporation (Sinopec)
3.5 .1
Sinopec is the largest producer and marketer of refined oil products in China and
Asia, and is the largest producer and distributor of petrochemicals in China. Sinopec
is a state-owned Chinese corporation, is the second largest oil and gas explorer in
China, and is the parent company of both TCC and SSEC China.
3.6
T he Zachry Group
3.6.1
The Zachry Group is an Alberta registered company that designs and manufactures
equipment fo r the oil and gas, pulp and paper, sawmill s and mining industries.
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September 27, 2007
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3. 7.
Zachry Energy International Inc.
3.7.1
Zachry Energy International Inc. is a British Columbia registered company that is
60% owned by the Zachry Group. Zachry Energy International Inc. provides
overview and management input to SSEC Canada and is 10% shareholder ofSSEC
Canada. Zachry International Inc. focused on helping SSEC China to liai se with
CNR L and to penetrate the oil and gas construction market in Alberta. T hey were
responsible to assist SSEC China to li aise with CNRL and assist with requirements of
training of the trade workers. They were responsible to assist SSEC China workers to
obtain work visas, and coordinated with Alberta Apprenticeship and Industry
Training (AA IT) requirements for designated trades. They assisted SSEC China to set
up SSEC Canada Ltd. , and assisted SSEC Canada Ltd. with obtaining legal counsel
to help the company deal with local regulations and laws in connection with their
establishment in Alberta. In March of 2007 Zachary Energy International Inc.
relinquished its 10% share of SSEC Canada. SSEC China and Sinopec requested that
Zachary Energy International Inc. be the lead contact for SSEC Canada in relation to
the investigation of WHSC with respect to the April 24, 2007 incident at the CNRL
Horizon site.
3.8
TIW Division of Canada Erectors Ltd. (TIW)
3.8. l
TIW is engaged in the fabricat ion, construction and distribution sectors of the steel
industry. TlW is a fully integrated unit for design, manufacturing, and construction of
fi eld erected steel platework structures. TIW was contracted byCN RL to provide the
components, material schedules for arrival on site, and the engineered drawings for
the 14 tanks on the east and west tank fanns at the CN RL Horizon plant site.
3 .8.2
The roof support structures were all fabricated " in house" by TIW at their faci Ii ties,
with the exception of the welding of columns to the cap plates, which was perfo1med
by Bartonair Fabrications of Hamilton. Bartonair is a regular supplier to TIW.
Bartonair was required to use TIW supplied materials, consumables and welding
procedures. TIW inspection personnel reviewed the materials before shipment. TIW
coordinated the identification, packaging and shipment of the roof support structures
(including columns) to the CNRL Horizon site.
Section 4.0
LOCATION OF INCIDENT
4.1
Tank 72-TK- l B, located on the west tank farm of the CNRL Horizon Oil Sands
Project, approximately 70 km north of Fort McMurray and 30 km north of Fort
MacKay, Alberta.
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Section 5.0
EQUIPMENT AND MATERIAL INVOLVED
5.1
The West Tank Farm
5 .1. I
The west tank farm is located approximatel y northwest of centre on the Hori zon Plant
Site. (Attachment "C", Site Layout). As the tanks had restricted means of entry and
exit and could become hazardous to workers entering them, they were designated as
confined space. Three high-cone steel tanks, Tank 72-TK-l A, 72-TK- IB and 72-TK1C are located on the west tank farm , in a line east to west with Tank 72-TK-1A at
the west, Tank 72-TK- lB in the centre and Tank 72-TK- lC at the east end of the row
of tanks. The tanks are all the same size and of the same construction. At the time of
the incident the roof support structure in tank 72-TK- l B was in a suspended state of
completion with the centre support column, the inside ring of 6 support columns and
the outer ring of 12 support columns in place, with the girders and rafters fitted,
waiting for the shell assembl y to be completed. Once the she ll assembl y was
completed, th e rafters from the outer ring's girders would be connected to the shell
wal1. T he roof support structure in tank 72-TK-1 B had been completed the day before
the collapse. At the time of the incident a team of boilermakers and scaffolders was
working in Tank 72-TK-1 C on the assembl y of the roof support structure.
(Attachment "A'', Photographs #1 1, # 15)
5.2
The East Tank Farm
5.2.1
The east tank farm is located at the east of the Horizon Plant Site (Attachment "C'',
Site Layout). When completed, the east tank farm will contain 10 tanks of various
sizes, and of generally similar construction to the tanks on the west tank fann . At the
time of the incident, the roof support structures in two tanks on the east tank farm,
Tank 73-TK-11 and 73-TK-12 were also in a suspended state of assembly waiting for
the shell walls to be competed. After which they would connect the rafters from the
outer rings' girders to the top of the shell walls. (Attachment "A", Photograph # 17)
5.3
Tank 72-TK-tB
5.3. 1
Tank 72 -TK-l B (described as a Dilbit Dewatering Tank), located on the west tank
farm, was to be a circular steel high-cone roo f tank, 56.5 mi n diameter and 19.8 m
high. At the time of the incident the tank wall shell was only completed to a height of
5.6 m . The tank structure consists of wall, fl oor and roof constructed from steel plate.
The roof is constructed onto a roof support structure cons isting of vertical circular
columns, supporting girders and radial rafters. (Attachment "D", Sketch of Roof
Support Structure). The components of the roof support structure are assembled
together with 19 mm (:X inch) nuts and bolts. At the time of the incident a team of
welders was working in the tank constructing the tank wall. T wo technicians were
also in the tank carrying out weld testing, and one scaffolder was in Tank 72-TK- l B.
T here was an Electri cal Consultant and a welding foreman who were checking out a
welding machine on top of the wall.
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September 27, 2007
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5.4
Assembly Procedure for Tanks
5.4. 1
SSEC Canada developed a procedure for assembling and supporting the tank roof
support structures for the tanks on the west tank farm. Erection of the shell was
independent of the roof support structure - they were being assembled concurrently.
The procedure consisted ofraising the centre support column first, using a crane and
securing it in the ve1iical positi on by workers operating elevating work platfo1ms to
install 4 steel cables, secured to the top of the column and anchored to lugs welded
onto the tank floor. The cables were tightened using "come-alongs". ("Come-along"
is a generic tenn to describe mechanical tensioning devices). The inner ring of 6
support columns was erected in a similar manner, but with 3 cables on each column.
The girders connecting the inner ring of columns were then lifted and bolted into
place, using 19 mm (:y.; inch) bolts, and the radial rafters were install ed between the
centre column and the inner ring. After the inner ring was completed, one cable,
extending towards the tank centre, was removed from each of the 6 inner ring
columns. The outer ring of 12 columns was erected, using 3 cables to support each
column. The girders connecting the outer ring of columns were lifted and bolted into
place, and all of the radial rafters were installed. After the outer ring of the roof
support structure was assembled, 6 steel cables were installed, extending from girders
to alternate columns in the outer ring to anchor lugs welded into the floor of the tank,
close to the tank wall. When these 6 support cables were in place and tightened using
"come-alongs'', all of the cables used to support the individual columns were
removed. The six cab les remaining were intended to support and stabilize the roof
support structure until the shell was completed to ful l height. The "come-alongs"
were removed after the cables had been tightened.
Section 6.0
NARRATIVE DESCRIPTION OF INCIDENT
6. 1
SSEC Canada recruited 132 Mandarin-speaking Chinese workers from TCC to work
as temporary foreign workers on the CNRL tank construction project. The workers
had at least 5 years experience as trades-people and had recei ved additional training
from a Canadian training agency before arriving in Canada. The workers started to
arrive in Canada in September of 2006.
6.2
On April 24, 2007, at the west tank farm, the roof support structures in tanks 72-TKlA (Attachment "A", Photograph #11) and 72-TK-lB were in the suspended state of
completion waiting for the shell to be assembled. Each roof support structure was
supported by six cables. The roof support structure in tank 72-TK-lC was being
assembled. The centre column and the inner ring had been completed and the steel
cables were still attached to the columns. No work was taking place in Tank 72-TKl A on April 24, 2007. A team of boilermakers was working in Tank 72-TK-I C,
assembling the roof suppo1t structure. (Attachment "A", Photograph # 15)
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September 27, 2007
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6.3
On April 24, 2007, a team of welders was working in tank 72-TK-1 B, welding
sections into the tank wall. The tank wall sections were being welded together by
welders and helpers working inside welding machines that tracked around the inside
of the tank wall. (Attachment "A", Photographs #2 0, #21) One Electrical Consultant
and a welder foreman were inside the tank checking an electrical fai lure on one of the
welding machines. One scaffolder was also on the floor area inside the tank. Two
weld test technicians were also in Tank 72-TK-1 B, testing and marking the welds on
the tank wall.
6.4
At approximately2:30 p.m. on April 24, 2007, workers inand around tank 72-TK- lB
heard several sounds, described as loud bangs or pops. The roof support structure in
tank 72-TK-1 B started to fal l in an easterly direction during windy conditions. As the
structure coll apsed, some of the support cables failed, many of the bolts that were
holding the components together failed and then the components began to come
apart. (Attachment "A", Photographs #8, #9, #10, # 22) The structure fell onto the
east side of the tank wall. Some of the components of the roof support structure can1e
to rest on the floor of the tank, some components came to rest lean ing against the
tank wall , and some components came to rest on the outside of the tank on the east
side. Many of the components were bent or damaged by the impact. After the roof
support structure collapsed some of the workers, who were in tank 72-TK-1 B,
managed to escape from the tank through manways or other holes in the tank wal I.
(Attachment "A", Photographs # 1, #2, #3, #4)
6.5
SSEC Canada workers from tank 72-TK-.1 C and other workers on the west tank farm,
as well as workers from other contractors who were working near the west tank fa1m,
went to tank 72-TK-lB to provide assistance. CNRL Horizon emergency services
were called and attended. Rescuers had to lift a large section of steel inside the tank
to remove the fatally injured Scaffolder. The Electrical Consultant was standing on
the top of a welding machine, which was located on top of the wall, and was fatally
injured when he was struck by falling steel. His body was thrown onto scaffolding
outside the tank. The Electrical Consultant was pronounced dead at the scene. The
Scaffolder, who was on the tank floor, was crushed by the falling steel and died in an
emergency conveyance vehicle on the way to Fort McMurray. Two other workers
received serious injuries and three more workers received minor inj uries. The two
seriously injured workers and two of the workers who had received minor injuries
were transported to hospital in Fort McMurray. The two seriously injured workers
were subsequently transferred to hospital in Edmonton.
6.6
INVESTIGATION OBSERVAT IONS AND IN FORMATION
6.6. 1
Workplace Health and Safety Compliance (WHSC) was notified of the incident by
CN RL Horizon at 3:08 p.m. on April 24, 2007. Workplace Health and Safety officers
from Fo1t McMurray were dispatched to the scene and while en route made contact
with RCMP Fort McMurray Detachment. WHSC officers arrived at the site at 5: 19
p.m. The scene had been secured by CNRL and RCMP.
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September 27, 2007
File: F-536919
6.6.2
WHSC issued a verbal Stop Work Order to CNRL at 8:36 p.m. on April 24, 2007.
The Stop Work Order was for construction of the three tanks on the west tank farm
and any similar tanks on the Horizon site.
6.6.3
On A pril 24, 2007 a WHSC Lead Investigator was dispatched from Edmonton to
direct the investigation. The Lead Investi gator atTived at the CNRL Horizon Oil
Sands Project at 9:00 a.m. on April 25, 2007. CN RL Horizon set up an internal
investigation team and met with the Lead Investigator and other Workplace Health
and Safety offi cers on April 25, 2007. The Lead Investigator confi rmed the verbal
Stop Work Order and reminded CNR L Horizon that no workers were to enter the
area and to have the area secured.
6.6.4
On A pril 25, 2007 a second WHSC Lead Investigator, the WH SC Manager of
Compliance, and an employee from another Govenunent of Albe1ta depa1tment, who
speaks Mandarin, were dispatched from Edmonton to assist with the investigation.
The second Lead Investigator, the Manager and the other employee arrived at the
CNRL Horizon plant site at 6:00 p.m.
6.6.5
It was found that there had been 13 workers inside tank 72-TK-lB at the time the
incident occurred. Ten workers were Chinese temporary foreign workers employed
by SSEC Canada, one Chinese worker (the Electrical Consultant) was directly
employed by TCC and two workers were Canadian workers employed by Iris NDT,
carrying out weld testing. All of the fatally injured and other injured workers were
Chinese temporary foreign workers. SSEC Canada workers and others who had
attended the scene were interviewed over a period of several days, in order to
determine the circumstances of the incident and the locations of all of the workers
who were inside the tank at the time of the incident. It was found that the workers
had carri ed out the assembly of the roof support structures in accordance with SSEC
Canada's chief engineer's instructions and the assembly drawings provided by T IW.
6.6.6
One of the fatally injured workers, an Electrical Consultant, had been on the top of a
welding machine working on the east side of the tank wall. The Electrical Consultant
had been struck in the head and back by a section of the falling steel and thrown onto
scaffolding outside the east wall of the tank. The other fatally injured worker, a
Scaffolder, had been standing on the tank floor, east of the tank centre, and had been
caught and crushed under a falling girder. Rescuers had manually lifted the girder to
rescue him. The Scaffolder died during transport to hospital. (Attachment "A",
Photographs #4, #5, #7)
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September 27, 2007
File: F-536919
6.6.7
One of the seriously injured workers, Welder l , had been inside the same welding
machine that the Electrical Consultant was working on. The welding machine })ad
been struck by fall ing steel and partially dislodged from the tank wall. Welder 1 was
trapped inside the welding machine and was rescued by CN RL staff and other
contract workers. The other seriously injured worker, Welder 2, was inside another
welding machine on the east wall that had been struck by falling steel and completely
dislodged from the wall, falling to the tank floor. Welder 2 was rescued by his
Chinese co-workers. (Attachment "A", Photographs #5, #6)
6.6.8
The verbal Stop Work Order was confirmed in writing on April 27, 2007. The Stop
Work Order prevented access to the east and west tank farms. The Stop Work Order
was re-issued on May 1, 2007 to define a specific part of the east tank farm around
tanks 73-TK-1 l and 73-TK 12 where workers could be at risk from the collapse of
the roof support structures. The remainder of the east tank farm was released to
CNRL. The Stop Work Order for the west tank farm remained in effect. CNRL
cooperated with the Stop Work Orders and provided barriers and security staff to
ensure that the order was made effective.
6.6.9
On May 12, 2007 the roof suppo1t structure in tank 72-TK-l A on the west tank farm
collapsed during windy conditions. The Stop Work Order was still in effect and no
workers were near the collapse. Before the collapse it had been observed that the roof
support structure was twisting during windy conditions. (Attachment "A",
Photographs # 18, # 19)
6.6.10
CNRL developed an engineered procedure for securing and dismantling the roof
support structures in tanks 73-TK-1 l and 73-TK-12 on the east tank farm. The Stop
Work Order for the east tank farm was lifted on May 16, 2007 and the site was
released to CNRL Horizon to enable the remediation work to be done. The work on
dismantling and removal of the roof support structures was completed on June 11 ,
2007 by SRS Industrial Services Ltd.
6.6.11
CNRL developed an engineered procedure for the removal of fallen materials in
tanks 72-TK-lA and 72-TK lB and the dismantling of the roof support structure
from tank 72-TK-l C. The Stop Work Order for the west tank farm was lifted on June
6, 2007. Work on tank 72-TK-I A commenced on June 8, 2007 and was compl eted on
June 13, 2007. Work then sta1ted on tank 72-TK-I B and was completed on June 20,
2007. The removal of the roof support structure in tank 72-TK-l C was completed on
June 22, 2007 by Penny Industrial Fabricators Ltd. The WHSC Lead Investigator
monitored the removal of the fallen materials from tanks 72-TK-1A and 72-TK-1 B
and during the removal retri eved material s from both tanks for analysis by an
independent consulting engineering firm.
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September 27, 2007
File: F-536919
Section 7.0
ANALYSIS
7 .1
Direct Cause
7 .1.1
Two workers working on the construction of a large steel tank 72-TK-1 B were fatally
injured, two other workers were seriously injured and three workers received minor
injuries when the roof support structure inside the tank collapsed suddenly and
without warning onto the workers.
7 .2
Contributing Factors
7 .2. 1
SSEC Canada assemb led the roof support structure as a stand alone structure, which
was not intended to be assembled as such by the T lW drawings. Neither CNRL nor
SSEC Canada consulted with TIW with respect to what assembly sequence should
be fo llowed for the construction of the roof support structure. As the erection of the
shell was independent of the roof support structure and they were being assembled
concun-ently, the top of the shell and the outer ring were not supporting each other.
7.2.2
TIW did not specify an erection sequence to follow to erect the tank they designed.
TIW did not specify the assembly sequence because that was not part of the contract
with CNRL.
7 .2.3
CNRL prepared a tank erection schedule specifying the sequence of construction
such as when the tank floors were to be laid, the walls to be started and the internal
roof support structures were to be erected. SSEC Canada followed the tank erection
schedule as set out by CNRL.
7.2.4
SSEC Canada did not provide written engineered erection procedures for the
assembly of the roof support structure. CNRL did not require SSEC Canada to
provide written engineered assembl y procedures.
7 .2.5
The SS EC Canada chief engineer who developed the erection procedure for the roof
suppo1i structures and specified the number, size and location of the guy wires was
not a qualified professional engineer.
7.2.6
The roof support structure was a completely bolted structure using ASTM A-307
Grade B bolts without the use of wedges or washers. The bolted roof support
structure, which was required to be flexible, did not have the necessary restraints to
resist the lateral forces generated by the wind.
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September 27. 2007
File: F-536919
7.2.7
The number and size of guy wires that were supporting the roof support structure in
tanks 72-TK- IA and 72-TK-1 B, was not designed for the static and dynamic loads
imposed by the 33 to 45 km/h wind that occurred on the day of the incident, let alone
for the maximum expected wind speed of 83 km/h, as determined by the Alberta
Building Code or 190 km/h recommended by the American Petroleum Institute.
(Attachment " A", Photographs # 12, #13, # 14, # 16)
7.2.8
There were six guy wires wrapped around girders located near the outer ring columns
to stabilize the roof support structure. Three of the guy wires were aligned in a rad ial
direction through the centre column axis; however, the other three guy wires were
significantly offset from radial alignment and were angled in the same direction by
14° to 24°. Because of the offset alignment, this action would result in forces
attempting to twist the roof support structure in a clockwise (easterly) direction,
which is the direction of the eventual collapse.
7.2.9
Because of the flexible bolted structure, any movement caused by the wind, would
provide means to loosen the nuts on the bolts as well as intensify the twisting force
on the guy wires.
7.2.10
Examination of the roof support structures in tanks 72-TK-1C, 73-TK-1 l and 73-TKl 2 showed that many of the bolts used to assemble the structures were loose; some
bolts had become bent during tightening, or necked because the thread length was to
short. o washers or bevelled washers were used in the assemb ly of the roof support
structure.
7.2.11
On April 25 , 2007 Workplace Health and Safety Compliance contracted Anderson
Associates Consulting Engineers Inc. to examine the circumstances leading to the
collapse of the roof support structure in tank 72-TK- l B. The Professional Engineer's
report summarized the following causes:
7.2.11.1
The collapse was primarily the result of inadequate guy wires used as wind bracing
on the partially assembled flexible roof structure. As wind speeds increased, the
flexible roof structure began to load the guy wires. Due to the structure's flexibility
and the unbalanced load conditions (the unbalanced geometry of the channel rafters
and the poor alignment of guy wires with the structure), the roof oscillated in the
wind. This movement of the 127 metric ton roof structure imparted cyclic loading
onto the guy wires. The upwind guy wire failed first as the wire rope clips became
overloaded and slipped toward the floor attachment lug. Once the structure was able
to move out of position, it collapsed in a downwind direction-essentially blown over.
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September 27, 2007
File: F-53691 9
7 .2. 11 .2
The design of the guy wire wind bracing was based on API 650 calculation methods.
These methods are inadequate for structural steel stability, although they are suitable
for their intended use (tank stability). As a result, the designer, who was not a
professional engineer, determined that there was minimal need for wind bracing.
Only six 12.5 mm (half inch) guy wires were used to brace the structure against wind
loads. These were neither aligned to prevent rotation of the structure nor sized with a
normal safety factor. When the wind speed increased, the structure began to oscillate
and the guy wires were overloaded by the inertia of the structural steel's movement.
7.2.11.3
Bracing to make the structure more rigid was not installed by the erector. This or
other temporary cross-bracing may have helped prevent or reduce the oscill ation that
led to the inertial load. More wind bracing, in tenn s of guy w ires or structural steel
cross-bracing, would have been required to prevent the incident.
7.2. 11 .4
The incident was not caused by material failure of the wire ropes, fi ttings or erection
equipment. Testing of the wire rope and wire rope clips confinned their design
capacity. Damage to the structural steel was all a result of the incident. The A-307 B
bolts used to connect the structural steel were proper strength when tested. They had
failed as the structure collapsed. It is unlikely that stronger bolts alone would have
provided the rigidity required to prevent the incident.
Section 8.0
APPLICABLE LEGISLATION
8.1
Occupational Health and Safety Act, Section 2(1)(a)(i)
Obligations of employers
8.1.1
SSEC Canada did not take reasonably practicable measures to protect the health and
safety of all the workers who were working inside the tank when the incident
occurred. The tank roof support structure that collapsed onto the workers was a
skeleton structure. The erection procedures for erecting the roof support structures
had not been prepared and certifi ed by a professional engineer.
8.1 .2
Tenth Construction Company of Sinopec (TCC) did not take reasonably practi cable
measures to protect the health and safety of the Electrical Consultant. The tank roof
support structure that collapsed onto the worker was a skeleton structure. The
erection procedures for erecting the roof support structures had not been prepared and
certified by a Professional Engineer. The Electrical Consultant did not have a work
permit as a temporary foreign worker and thus should not have been working at this
work site.
14
September 27, 2007
File: F-536919
8.2
Occupational Health and Safety Act, Section 3(3)
Prime Contractor
8.2. 1
CNRL did not do what was reasonable and practicable to ensure the Act and the
regulations were complied with by failing to ensure that one of their contractors had
erection drawings and procedures for a skeleton structure certified by a professional
engrneer.
8.3
Occupational Health and Safety Regulation, Section 7(1)
Availability of specifications
8.3. 1
The Occupational Health and Safety Code requires skeleton structures to be erected
in accordance with engineered erection procedures. SSEC Canada did not provide
engineered erection procedures. The procedures for the erection of the roof suppo1i
structure were not certified by a professional engineer and the specifications were not
readily available to the workers responsible for the work. The workers were given
only verbal instructions on the erection procedure.
8.4
Occupational Health and Safety Regulation, Section 13(1)(a)(b)
General protection of workers
8.4. 1
SSEC Canada did not ensure that the engineer who developed the erection drawings
and proced ures of the roof support structure was a professional engineer competent to
do the work, or supervised by a professional engineer.
8.5
Occupational Health and Safety Code, Section 7(1)
Hazard assessment
8.5.1
SSEC Canada held daily too lbox meetings before work started. Field level risk
assessments were carried out during the toolbox meetings. SSEC Canada had
prepared a HSE Manual containing generic safety procedures.
8.6
Occupational Health and Safety Code, Section 14(1)
Certification by a professional engineer
8.6.1
The Code requires that skeleton structures are erected in accordance with erection
procedures certified by a professional engineer. SSEC Canada did not ensure that the
erection p rocedure and drawings had been certified, signed and stamped by a
professional engineer.
15
September 27, 2007
File: F-536919
8.7
Occupational health and Safety Code, Section 46(3)
Confined space training
8.7.1
SSEC Canada did not ensure that the worker who was assigned duties relating to
confined space entry was trained by a competent person. The worker who had been
designated the Confined Space Monitor for the day of the incident was not aware of
the purpose of the confined space designation, his duties in terms of maintaining
communication w ith the workers in the confined space, or his duties if an emergency
occurred. The Confined Space Monitor had not been effectively trained in his duties
and was not competent to perfonn the duties required . The Confined Space Monitor
was not able to communicate with the workers inside the tank and was not able to
rai se an alarm following the incident.
8.8
Occupational Health and Safety Code, Section 55(1)
Confined space emergency response
8.8. 1
SSEC Canada had an emergency response procedure. However, on the day of the
incident the worker who had been designated as the Confined Space Monitor was not
aware of the emergency response requirements and was not capabl e of raising an
alarm or implementing an effective rescue. SSEC Canada did not ensure that the
emergency response plan included procedures to evacuate the confined space
immediately.
8.9
Occupational Health and Safety Code, Section 56(1)
Confined space tending worker
8.9.1
The worker who had been designated as the Confined Space Monitor was not
competent. SSEC Canada did not designate a competent worker to be in
communication with the workers in the confined space.
8. 10
Occupational Health and Safety Code, Section 56(2)
Confined space tending worker
8.10. 1
On the day of the incident the worker who was the Confined Space Monitor did not
have a telephone or radio to summo n assistance. SSEC Canada did not ensure that
the designated worker had a suitable system for summoning assistance.
8. 11
Occupational Health and Safety Code, Section 190(1)
Skeleton structures
8.1 1.1
SSEC Canada did not ensure that erection drawing and procedures for the erection of
the roof support structure in tank 72-TK- I B were prepared and certified by a
professional engineer.
16
September 27, 2007
File: F-536919
8. 12
Occupational Health and Safety Code, Section l90(2)
Skeleton structures
8.1 2. 1
The erection procedure prepared by SSEC Canada for the erection of the roof suppo1i
stmcture in tank 72-TK-1 B did not ensure that the structure was stable during
assembly.
8.13
Occupational Health and Safety Code, Section 300(1)
Cable clips
8.13. 1
SSEC Canada did not ensure that u-bolt type clips used for fasteni ng wire rope were
installed so that the u-bolt section of the clip bears on the dead side of the rope and
the saddle of the clip bears on the li ve side of the rope.
8.1 4
Occupational Health and Safety Code, Section 306(1)
Wire rope
8.14.1
SSEC Canada did not remove from service wire rope used to support the roof support
structure in tank 72-TK- l B that had been distorted because of kinking where it had
been attached around girders.
Section 9.0
FOLLOW-U P I ACTION TAKEN
9. 1
Alberta Employmen4 Immigration & Industry
9.1. I
WHSC issued Stop Work Orders to CNRL for the construction of the east and west
tank farms. WHSC issued orders for securing and dismantling the roof support
structures in the east and west tank farm. Orders were issued for remedial actions to
remove fa llen rnate1ial in tanks 1A and 1B. Orders were also issued for
documentation, hazard assessments and for an investigation repoti.
9. 1.2
WHSC issued orders to SSEC Canada to provide documentation such as, worker
information, worker training records, hazard assessment and engineering procedures.
Orders were also issued to SS EC Canada to cooperate with CNRL's incident
investigation.
9. 1.3
WH SC issued orders to TIW to provide the tank drawing specifications, assembly
instructions, component testing and contact information with SSEC Canada.
9. 1.4
WHSC issued orders to ewfab Industries Ltd. to provide written observations from
the disassembly of the roof support structure in tank 72-TK- 1C.
17
September 27. 2007
File: F-5369 19
9.1.5
WHSC issued orders to SRS Industrial Services for written observations from the
securing and the dismantling of the roof support structures in tanks 73 -TK-1 1 and
73-TK-1 2.
9.2
Industry
9.2.1
At this time, CNRL has complied with all of the written orders with the exception of
the order pertaining to the completi on of an incident investigation report.
9.2.2
SSEC Canada complied with all of the orders written.
9.2.3
TIW complied with all of the orders written.
9.2.4
Newfab Industries Ltd. compli ed with all of the orders written.
9.2.5
SRS Industrial Services complied with all of the orders written.
9.3
Additional Measures
9.3 .1
o additional measures were required.
Section 10.0 SIGNATURES
.>"'"~
A7 6J.c:>o7
D e
J
Se:P1e~eisi? 21- . k~.
Date
~Z2Po7
Date
../
Section 11.0
ATTACHMENTS
Attachment "A"
Attachment "B"
A ttachment "C"
Attachment "D"
Photographs
Location Map
Site Layout
Sketch of Roof Support Structure
18
September 27, 2007
File: F-536919
Attachment "A"
Page 1of22
Photograph #1
Shows the debris field on the east side of tank 72-TK lB
after the collapse of the tank roof support structure.
File: F-536919
Attachment "A"
Page 2 of22
Photograph #2
Shows part of the debris field on the outside of tank 72-TKlB after the collapse. Arrow "A" indicates the top of the
welding machine where the Electrical Consultant was
standing when he was struck by the collapsing steel. Arrow
"B" indicates where the Electrical Consultant's body was
found.
File: F-536919
Attachment "A"
Page 3 of22
Photograph #3
Shows the interior of tank 72-TK- l B after the collapse of
the roof support structure. This image was computer
generated from several photographs. Arrows "A" indicate
one of the vertical columns in the outer ring, and the base
where it was standing before the collapse. Arrows "B"
indicate one of the vertical columns in the inner ring and its
base.
File: F-536919
Attachment "A"
Page 4 of22
Photograph #4
Shows the interior of tank 72-TK-lB after the collapse of
the roof support structure. Arrow "A" indicates the centre
support column. Arrow "B" indicates the hard hat that was
worn by the Scaffolder.
File: F-536919
Attachment "A"
Page 5 of22
Photograph #5
Shows the interior of tank 72-TK-lB after the collapse of
the roof support structure. Arrow "A" indicates the welding
machine partially dislodged from the tank wall that the
Electrical Consultant was standing on, and Welder 1 was
working in, at the time of the incident. Arrow "B" indicates
the welding machine that fell from the tank wall, that
Welder 2 was working in.
File: F-536919
Attachment "A"
Page 6 of22
Photograph #6
Shows a closeup view of the welding machine that Welder 2
was working in.
File: F-5 36919
Attachment "A"
Page 7 of22
Photograph #7
Shows a closeup view of the welding machine that the
Electrical Consultant was standing on, and that Welder 1
was working in.
File: F-536919
Attachment "A"
Page 8 of22
Photograph #8
Shows part of the collapsed structure from tank 72-TK-lB,
showing one of the % inch bolts that were used to bolt the
components of the roof support structure together.
File: F-536919
Attachment "A"
Page 9 of22
Photograph #9
Shows a sheared 14 inch bolt on the ground to the east of
tank 72-TK-lB.
File: F-536919
Attachment " A"
Page 10 of22
Photograph #10
Shows the bolt also shown in photograph 9. The markings
on the bolt head indicating the specification of the bolt, A307-B, can be seen.
File: F-536919
Attachment "A"
Page 11 of22
Photograph #11
Shows the completed roof support structure in tank 72-TKlA, before it also collapsed. The roof structure that
collapsed in tank 72-TK-lB was identical to this. Arrow
indicates one of the support cables.
File: F-5 36919
Attachment "A"
Page 12 of22
Photograph #12
Shows a closeup of one of the support cable top connections
on tank 72-TK-1 A. Arrow "A" indicates where the support
cable has been secured back onto itself using a screw pin
shackle. Arrow "B" shows the top connection of one of the
cables that had been used to support the vertical column
during the erection of the roof support structure. This cable
had not been removed after the assembly of the structure
was completed.
File: F-536919
Attachment "A"
Page 13 of22
Photograph #13
Shows the top connection of another support cable on tank
72-TK- lA. Arrow indicates where the cable is kinked as it
passes over the top plate of the column.
File: F-536919
Attachment "A"
Page 14of22
Photograph #14
Shows a beam from tank 72-TK-lB after the collapse of the
roopf support structure. The top end of one of the support
cables is still attached to the beam. Arrow indicates where
the cable has been kinked and distorted as it passed through
the shackle.
File: F-5 36919
Attachment "A"
Page 15 of22
Photograph #15
Shows the partially completed roof structure in tank 72-TKl C. The cables used to support the vertical columns can be
seen. The centre column and the inner ring of 6 columns
have been erected, the beams have been installed joining the
inner ring, and some of the radial purl ins have been
installed.
File: F-536919
Attachment "A"
Page 16 of22
Photograph #16
Shows the base of the centre column in tank 72-TK-lC. The
"come-alongs" tensioning the cable supporting the columns
can be seen. Arrow "A" indicates a cable that has been
clamped correctly, with the saddle clamps installed so that
the saddles are on the live side of the cable. Arrow "B"
shows one that has been made up incorrectly, with the
saddles on the dead side of the cable.
File: F-536919
Attachment "A"
Page 17of22
Photograph # 17
Shows tanks 73-TK-l land 73-TK-1 2 on the east tank farm.
These tanks are smaller than the tanks on the west tank
farm . The roof support structures consist of a centre colwnn
and one ring of 6 columns. The roof support structure
installation has been completed and the support cables can
be seen.
File: F-536919
Attachment "A"
Page 18of22
Photograph #18
Shows the debris field on the east side of tank 72-TK-lA
after the roof support structure in this tank also collapsed.
File: F-536919
Attachment "A"
Page 19 of22
--
:
Photograph #19
..... ,
Shows the collapsed roof support structure on the east side
of tank 72-TK-lA. It can be seen that several tank wall
sections were broken off this tank during the collapse.
File: F-536919
Attachment "A"
Page 20 of22
Photograph #20
Shows an intact orbital welding machine on the inside of a
tank wall. A welder working inside the welding machine
would be welding the horizontal seam indicated by the
arrow.
File: F-536919
Attachment "A"
Page 21 of 22
k,.
Photograph #21
Shows an intact orbital welding machine seen from outside
the tanlc The work platform on the top of the welding
machine can be seen. The Electrical Consultant was
standing on the top work platform of a similar welding
machine at the time of the incident.
File: F-536919
Attachment "A"
Page 22 of22
Photograph #22
Shows the lower end of one of the cables supporting the
roof support structure in Tank 72-TK-lB after the collapse
of the structure.
File Number: F-536919
Attachment: "B"
Location Map
Not to Scale
N
•
..s
Jort
McMa rraiiJ
File Number: F-536919
Attachment: "C"
Site Layout
Not to Scale
Camp3
Lodge
\ To Aerodrome 5km
Sulphur Recovery:
Coker I Diluent Reco"ery
¢
Cogeneratlon Plant and Utilities
N
w
WestTank Farm
s
Ad min I Warehousing
ast Tank Farm
Hydrogen Plant
Hydrotreatin g
Heat Integration
\Froth Treatment
Mine Maintenance and
Administration Facilities
--
To South Mine
D
Phase: D
PllSlse 2
F-536919
Attachment "D"
Sketch of roof support
structure
Not to scale
TANK SHELL
OUTER RING
GIRDERS
~
INNER
RING
GIRDERS
- .... -
1
GUY
WIRES
OUTER
RING
SUPPORT
COLUMN
ELEVATION
TANK
SHELL
INNER RING
SUPPORT COLUMN
CENTRE SUPPORT
COLUMN
GUY WIRES